The 35-acre campus is an island of young people, where teens and 20-somethings outnumber grown-ups by 10-to-1.

The place is awash in fresh-faced students, and even the workers — from the cafeteria to the copy center, the mailroom to the bookstore — and most of the teachers are under 30.

It’s no “Animal House,” though, with raucous frats, food fights and binge drinking. This is Mormonism’s elite Missionary Training Center, where the men wear white shirts and ties, the women don modest skirts and dresses and everyone is expected to heed the rules.

It ranks second among the nation’s largest on-site language schools, behind only the U.S. Defense Department’s Language Institute in Monterey, Calif.

Mormons have “perfected their language training through years and years of experience and feedback,” says Col. Derek Tolman, commander of Utah National Guard’s linguistic unit, who is familiar with both systems. “The Missionary Training Center is excellent at teaching the fundamentals in a short time.”

But the MTC, as it is known, teaches much more than diction and dialects. It’s the place, just north of Brigham Young University, where young Latter-day Saints are molded and mentored. It’s the place they are built up and, sometimes, dressed down.

It’s where they start to learn the languages (55 in all) they will need to preach the Mormon message and where they begin to bolster the faith they will rely on to sustain the rigors of missionary life — from 6:30 a.m. wake-ups to 10:30 p.m. lights out — every day for 24 months (18 months for women).

From the moment they arrive, the newly minted missionaries are never alone; they’re assigned a same-gender “companion” who’s going to the same mission who will be with them at all times. They are not allowed to phone home, chat with friends on the Internet, watch TV or non-Mormon videos, read a novel or a newspaper, or listen to popular music. There’s no sex or dating.

The MTC is boot camp, two to nine weeks (depending on the mission destination) of intense language study and gospel grounding. From there, these foot soldiers of Mormonism will ship out for stations around the globe, out to convert the world.

And now the Provo MTC is the epicenter of a historic surge.

Since last October, when the Church of Jesus Christ of Latter-day Saints lowered the age for male missionaries from 19 to 18 and for females from 21 to 19, their ranks have skyrocketed. “Sister” missionaries now make up 42 percent of the enlistees, up from the 10 percent to 15 percent before the age change.

Built in the 1970s to house about 2,300 missionaries, the facility now has about 3,500 residents, with nearly 900 new ones arriving every Wednesday at a rate of 100 cars every 15 minutes.

This explosion of would-be proselytizers has required adding bunk beds to dorm rooms that were created for four and now are equipped for six. It has meant hiring a wave of new language teachers, who are all recently returned missionaries, bringing the total to 1,200, up from 800 just a year ago.

“Approximately a quarter of the current MTC teachers are women,” says church spokeswoman Ruth Todd. “The church seeks to hire only the best candidates to serve there.”

Mealtimes are staggered in the 800-seat cafeteria, which serves 10,000 meals a day and caters to carnivores, vegans, picky eaters and those on strict gluten-free diets. A single mailroom processes about 6,000 letters and packages on an average Monday, including some 5,000 printed emails going through dearelder.com.

“You don’t want to be here on Valentine’s Day,” said Heidi Van Woerkom, who has supervised the MTC mailroom for 22 years. “We get about 13,000 packages coming in.”

Despite the numbers and frenetic pace, a sense of calm and order pervades the hallways of the center’s 19 buildings. MTC President Lon Nally says the vast majority of incoming missionaries “love what they’re doing.”

“They are smart, energized and happy,” says Nally, who has been on the job since January, “and full of faith.”

That’s a good thing. Otherwise it could be hard to survive such a demanding load.

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Missionaries learning one of the 55 languages typically spend eight to nine weeks there. Those learning Romance languages such as Spanish, French and Italian stay six weeks, and those going to English-speaking missions leave after two weeks, except for those learning English as a second or third language.

The schedule is essentially the same for everyone: three meals a day, one hour of physical activity, and about 10 to 12 hours of language or religious training. Church services are held on Sunday and devotionals with church leaders on Tuesday. Missionaries also have a day off to do laundry, write letters home and attend the nearby Provo temple.

Though it seems like a one-size-fits-all approach, the training can adapt to any missionary’s skills and needs, says Spencer Christensen, the MTC’s operations manager.

The system works, Nally and others say, because it is based on missionaries helping one another rather than competing, and because the teachers are more like peers than pedagogues.

“What makes the MTC so unique, and so effective in teaching languages, is that the teachers are returned missionaries who have gone through the same process,” said Ami Zahajko, a Mormon mom in Seattle, who taught Russian at the MTC five years ago. “They are able to meet individual needs of missionaries. They have a lot of empathy.”

The classes are small — eight to 12 missionaries in each — and use mostly the language of faith for their curriculum. Missionaries learn to pray and preach in the new language before they learn common phrases such as “happy birthday” or “Where is the bathroom?”

Learning the language is the “most difficult part” of the MTC, says Elizabeth Stevenson, of Montana, who is studying Thai. But it helps, she said, when native language speakers who live in Utah come to class to engage the students as if they were “investigators,” or potential converts.

“I learned more Spanish here than sitting in a high-school class for two years,” said Jessica Howard, of King City, Calif., who is headed to Argentina. “It is really helpful to hear natives speak.”

But, she added, the Holy Spirit is the “real teacher.”

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It takes detailed planning, logistical wizardry and quick responses to make the MTC run smoothly, from reacting to medical emergencies to forgotten passports, visa headaches, legal entanglements and family dramas.

Plus, the system is always trying to adapt to 18-year-olds who have never lived away from home. Don’t put your suits in the washing machines, warns a sign posted in the laundry room.

The campus is governed by a clear male hierarchy with Nally at the top and his two “counselors,” as in any Mormon presidency. The MTC also is parceled into six “districts,” each with its own full-time adult leader.

Missionaries are further divvied into language-speaking “zones” and “districts” for their training. Those correspond to small ecclesiastical units, known as branches. Each of the MTC’s 75 branches has 30 to 50 members, supervised by a branch president and two counselors.

These branch presidents and their wives are available on Tuesday and Thursday evenings for counseling — and lots of young people seek it.

“Homesickness is a real issue,” says Margaret Young, a BYU professor whose husband, Bruce, served as a counselor in a French-speaking MTC branch from 2008 to 2010. “We did lose a few to anxiety.”

Most didn’t realize they would have a problem until they got to Provo, Young said. Then they questioned whether they would be able to learn the language or whether they had what it takes to be a missionary.

Some young people resent the center’s structure and all the rules; others wrestle with their faith.

But the system is not set up for failure and not many do, Nally said, estimating that fewer than 0.05 percent leave, and that number includes all those facing language, medical, emotional or spiritual issues.

The MTC produces “an extreme sense of unity,” Young said. “You put a group of people in a survival situation and they will bond.”